Benefits of providing cognitive performance strategies to novice performers learning a complex motor skill.

Verbal reports were collected from experienced performers during acquisition trials of a novel throwing task and summarized as cognitive performance strategies. These strategies were incorporated in the practice regimen of 8 novices with no sport experience who learned the same task. A control group of 8 novices practiced the task without the experts' cognitive performance strategies. The performance of the novices who used the strategies was similar to that of the experts and significantly better than the performance of the control novices.

Investigation of the contextual interference effect in the manipulation of the motor parameter of over-all force.

This investigation examined the contextual interference effect when manipulating over-all force in a golf-putting task. Undergraduate women (N = 30) were randomly assigned to a Random, Blocked-Random, or Blocked practice condition and practiced golf putting from distances of 2.43 m, 3.95 m, and 5.47 m during acquisition. Subjects in the Random condition practiced trials in a quasirandom sequence and those in the Blocked-Random condition practiced trials initially in a blocked sequence with the remainder of the trials practiced in a quasirandom sequence. In the Blocked condition subjects practiced trials in a blocked sequence. A 24-hr. transfer test consisted of 30 trials with 10 trials each from 1.67 m, 3.19 m, and 6.23 m. Transfer scores supported the Magill and Hall (1990) hypothesis that, when task variations involve learning parameters of a generalized motor program, the benefit of random practice over blocked practice would not be found.

Using bandwidth knowledge of results to alter relative frequencies during motor skill acquisition.

This investigation examined the predictions of the guidance and specificity hypotheses by manipulating different distributions of relative frequency of knowledge of results (KR) using bandwidth (BW) conditions. Subjects (N = 120) were randomly assigned to either a BW0%, BW10%, Shrinking-BW, or Expanding-BW condition. After 100 acquisition trials were completed, a double transfer design was employed in which the subjects were divided in half and randomly assigned to a no-KR or KR retention condition. Retention tests of 10 min and 48 hr were completed under a no-KR or KR retention condition. Results of the 48-hr retention test under the no-KR retention condition suggested that receiving high relative frequencies of KR at the end of the acquisition phase was as detrimental to motor skill learning as receiving high relative frequencies of KR throughout acquisition. The results are discussed with respect to the guidance and specificity hypotheses.

On the psychophysics of arm-positioning movements.

The basis for the relationship between physical stimulus and magnitude of psychological response in angular movements of the upper limbs was investigated. Participants compared movements to a standard location with movements to comparison locations and movements of a standard distance with movements of comparison distances. The results add to the controversy surrounding the explanations for the differences in psychological response magnitude of movements to locations and movements across distances. Data obtained from movements to locations and movements across distances indicated similar Weber ratios but different patterns for the just noticeable differences. The data of this and previous research suggest that the application of a prothetic continuum to arm movements is inappropriate. An alternative explanation of the differences in the perception of movements to locations and movements across distances is offered.

Improved foot position sense as a result of repetitions in older adults.

This research investigated whether acuity of perceived foot position changes as a result of repetitions in older and young adults. Subjects actively held four reference positions with one foot and matched these positions 12 times with the other foot. The data suggest that young adults performed the matching tasks with more overall accuracy and less variability than the older adults. Both young and older adults needed progressively less time to perceive an accurate match with repetitions. Repeated matching trials improved performance consistency in the older adults and resulted in less bias in both age groups. These results imply that adult aging affects the quality of the sensory signals conveying foot position at the ankle joint, but that repetitions make older adults more aware of proprioceptive feedback resulting in faster, more consistent, and more accurate performance.

Age-related differences in the control of spatial aiming movements.

The experiment was designed to (a) examine age-related differences in the control of aiming movements, and (b) determine the locus of slowing in movement execution of older adults. Fitts's (1954) index of difficulty (ID) was used to manipulate movement execution demands, and kinematics were used to examine the response characteristics. Twelve young and 12 older adults performed simple aiming movements 10 cm or 20 cm in amplitude to targets of 0.5 cm, 1.0 cm, or 2.0 cm in width, resulting in IDs ranging from 3.32 to 6.32. The results for both young and older subjects support the prediction that movement time (MT) increases as a function of ID and that older adults are significantly slower and more affected by increases in ID than the young adults. Velocity and acceleration profiles of the older adults' movements displayed very different response characteristics than those of the young adults. The results suggest that older adults emphasize accuracy of response and are concerned with the latter phase of the movement in order to contact a target accurately.

Changing affordances in stair climbing: the perception of maximum climbability in young and older adults.

This experiment extended Warren's leg-length model by investigating the relevance of leg strength and joint flexibility on perceptual judgments of climbability. From a set of 8 stairs (riser heights: 38-91 cm), 24 older and 24 young adults were asked to identify the highest stair they could climb without using their hands or knees. Ss then attempted to climb the selected stair. Tall and short young observers perceived similar action boundaries despite leg-length differences. Tall and short older adults had divergent action boundaries when a single-scale leg-length model was applied. A regression model that used flexibility and leg-strength measurements provided a better fit of the older adult data, indicating that models applying functional (kinematic and kinetic) criteria might be useful in describing lawful relationships between organisms and the environment.

Psychophysics of arm movements and human aging.

The purpose of this study was to investigate possible age-related differences in the physical stimulus-psychological response relationship. Young and older adult subjects moved their arm to three standard locations or extents (25 cm, 50 cm, and 75 cm) on a linear positioning device. Seven standard comparison combinations were presented 20 times each. Subjects were asked to determine whether the comparison was different from the standard. Just noticeable difference, constant error, absolute constant error, and Weber ratios were calculated. In contrast to previous studies, the results clearly indicate that the physical stimulus-psychological response magnitude relationship for location and extent movements is best described by a metathetic continuum. We offer an explanation to account for the differences between location and extent movements for the just noticeable difference and Weber ratio. The failure to find differences between the age groups suggests that age-related declines cannot be generalized to all perceptual systems.

Variables affecting perceptual boundaries in bipedal stair climbing.

The present study examined the effects of hip joint mobility and relative leg strength on perceived and attained action boundaries in bipedal stair climbing. If action boundaries are directly perceived and action is intimately linked to perception, one should be able to quantify these boundaries (Warren, 1984) and identify what variables affect these perceived boundaries. In the present experiment the perceived and attained absolute and relative (riser height divided by leg length) action boundaries were significantly affected by hip joint flexibility. Relative leg strength also affected absolute and relative perceived action boundaries. These results clearly show that factors in addition to body size and body proportions may affect the perception of affordances and their boundaries.

Age differences in visual sensory integration.

Numerous authors have reported that elderly persons are more affected than young adults when submitted to reduced or conflicting sensory inputs conditions. These results, however, do not permit to evaluate whether the elderly suffer from a reduced peripheral sensibility or from a deficit in the central integrative mechanisms responsible for configuring the postural set. The present experiment evaluated the ability of elderly to reconfigure the postural set when submitted to successive reduced and augmented visual sensory conditions. Results showed that young and elderly subjects' sway dispersion increased when they were exposed to a reduced visual sensory condition (i.e., vision/no-vision transition). However, when exposed to augmented sensory condition (i.e., no-vision/vision transitions) young adult were able to adapt rapidly and reduced their sway dispersion whereas the elderly exhibited an increased sway dispersion. This inability to adapt to an augmented sensory condition suggest that elderly persons, in addition to a reduced peripheral sensibility, have a deficit with central integrative mechanisms responsible for reconfiguring the postural set.